Fix #15925: Include lyrics in MIDI export

[bakajikara]

Resolves: #15925

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[Jojo-Schmitz]

Could this one get reviewed please?

[mikekirin]

Looks like memory leak here. According to the fact that this code used in the loop there is huge memory leak possible =)
Isn't there a method in mu::String which returns char*?

[Jojo-Schmitz]

Or just delete[] data; at the end of that loop

[cbjeukendrup]

Note that this method is full of similar memory leaks, therefore I ignored it while reviewing.

Isn't there a method in mu::String which returns char*?

No, because mu::String uses utf16 so if you want char* you need to convert.

Or just delete[] data; at the end of that loop

Hell no 😄 because we're storing a pointer to it in the resulting MidiEvent.

I think the conclusion is that we should refactor to avoid the need for char*, and store it differently in MidiEvent.

[mikekirin]

size_t len = lyricText.size(); // Not sure + 1 is necessary. If so it should be data[len] = '\0', otherwise it's undefined

However why not to use easier approach without unnecessary memory allocation?

std::string lyricText = lyric->plainText().toStdString();
size_t len = lyricText.size();
ev.setEData(lyricText.c_str());
ev.setLen(static_cast<int>(len));

[mikekirin]

Hell no 😄 because we're storing a pointer to it in the resulting MidiEvent.

Good point

[Jojo-Schmitz]

ev.setEData(lyricText.c_str());

c_str() is not an unsigned char * like setEData() expects, seems some casting is needed

[Jojo-Schmitz]

But even with that it just doesn't work, on importing such a MIDI the lyrics are completly broken
Actually always the same syllable, but even that sometimes trunccated

[cbjeukendrup]

size_t len = lyricText.size(); // Not sure + 1 is necessary. If so it should be data[len] = '\0', otherwise it's undefined

However why not to use easier approach without unnecessary memory allocation?

std::string lyricText = lyric->plainText().toStdString();
size_t len = lyricText.size();
ev.setEData(lyricText.c_str());
ev.setLen(static_cast<int>(len));

That's basically equivalent to using delete: as soon as lyricText goes out of scope, the underlying c string is deleted but the MidiEvent still contains a pointer to it. That's probably why the result is "completely broken" on Windows and would cause Address Sanitizer complaints on macOS/Linux.